In London air travelers undergo a body search and a photo-identification check and answer questions about the contents of their baggage. In most airports in Arab nations, passengers must personally identify their luggage on the tarmac before it is loaded onto the airplane. In Beirut travelers clear no fewer than 14 checkpoints to reach their airplane seats. And before boarding a flight of the Israeli airline El Al, anywhere in the world, passengers have their baggage thoroughly searched and answer dozens of detailed personal questions ranging from where they stayed the night before to the names and nationalities of their parents. Even Athens' Hellinikon airport, criticized by U.S. aviation authorities this year for lax security procedures and the previous stop of the TWA Boeing 747 before its ill-fated departure from New York City last week, requires that passengers be screened at least twice, by Greek security and again by airline officials.

Before the TWA disaster, travelers on U.S. airlines seldom faced that kind of scrutiny. But if terrorism turns out to be the cause of the crash, Americans may have to live with the higher levels of security that are already routine in much of the world.

"Many, many more security checks are performed in Europe than in the U.S., because the terrorism threat exists here. [Security forces] are on very high alert at all times," says a senior official at the Federal Aviation Administration's regional office for Europe, the Middle East and Africa. Since the 1988 downing of Pan Am Flight 103 over Lockerbie, Scotland, and the similar destruction of a French passenger jet in Niger months later, European governments and airlines have instituted an imposing array of security checks to prevent a repetition. They range from simple hand searches to probes with highly sophisticated scanners capable of detecting virtually any kind of explosive device. "You are interviewed both at check-in and boarding gates, and there are many other procedures behind the scenes that passengers aren't aware of," says the FAA security official. "There is control of checked luggage, control of carry-on baggage, control of everything that goes onto the aircraft, including cargo and catering."

Despite the shock of the Lockerbie bombing, few American airports require anything close to that level of security. Most of the latest bomb-screening equipment, developed and built by American companies, is being sold to airports in Europe. Even such rudimentary precautions as "positive bag matching"--making sure that all passengers who checked baggage are on board the plane--is applied only to international flights. Security specialists are alarmed at the low pay and poor morale of airport-security workers, and at the ease with which undercover investigators are able to breach physical barriers. "Our security system," says Billie Vincent, who was head of FAA security from 1982 to 1986, "is not a model that one would hold up with any pride."

That is partly because American security is still largely in the hands of the air carriers and airport authorities, who hire and supervise the personnel charged with insuring safety, as opposed to the civil-service professionals employed in most other countries. The FAA gently prods the airlines to strengthen safeguards, but it does not push aggressively because they increase costs in one of the most intensely competitive industries in the world. Often the industry is reluctant to make the changes even after intelligence agencies issue specific warnings. When the CIA last summer reported signs of increased terrorist threats to U.S. airlines, the FAA proposed that positive bag matches be required for domestic flights. But the Air Transport Association, an industry trade group, vigorously opposed it on the grounds that it would cost too much--at least $2 billion to implement the program, according to an FAA estimate--and cause unacceptable delays.

Because it was an international flight, however, bags for Flight 800 were matched with passengers, perhaps suggesting even that precaution may not be enough to prevent bombings. The policy assumes terrorists would be unwilling to be blown up with their own bomb. But as was shown in the 1983 bombing of a U.S. Marine barracks in Beirut and similar attacks in Israel recently, fanatical bombers may be prepared to sacrifice their own lives for what they view as a holy cause. "We've been going through a transition," says one U.S. intelligence official. "First we had the hijacker threat. The next evolution was the unaccompanied bag aboard a plane that had a bomb inside. Now the next threat may be the suicide bomber aboard the airliner."

After the Lockerbie crash, caused by a bomb put inside a piece of unaccompanied luggage, Congress ordered the FAA to speed up research on equipment to detect explosives and on blast-resistant cargo boxes. But the FAA was slow to respond, and the industry resisted change because of costs. Cargo boxes made with anti-blast plastics--or, alternately, made in such a way as to help dissipate the explosion of a small bomb--would cut the carrying capacity of cargo holds by 5% or more and add about $50 to the price of a round-trip economy-class transatlantic ticket.

Progress has been nearly as slow on bomb-detection equipment. While a variety of new devices have been installed in airports abroad, the FAA has so far certified only one for evaluation. "We would like to have a magic box that would detect explosives and work efficiently," says Tim Neale, an ATA spokesman. "But no such device has been proved." The FAA standard calls for the ability to examine 600 pieces of baggage per hour and to detect a wide range of explosives while producing no more than a 10% rate of false alarms.

The one piece of advanced equipment certified by the FAA operates like a medical CT scanner, examining and analyzing the molecular structure of materials inside a bag to determine whether explosives are present. A California firm, InVision Technologies, began making the machines in 1993, but only three have been purchased for use in U.S. airports--one in San Francisco and two in Atlanta. Meanwhile, airports in Asia and Europe are clamoring for the equipment, and the rest of InVision's production so far, some 20 units, has gone to airports in Brussels, London, Manchester and Manila. Sluggish U.S. interest is partly the result of price. Each unit costs nearly $1 million, and a busy airport would need as many as 30 to inspect all bags. Still, major airports in other developed countries are spending money on that and other technologies little used by U.S. airports.

A report earlier this year by the U.S. General Accounting Office said the FAA has declined to require improved screening devices such as InVision's because of cost. "Other countries, such as the United Kingdom and France, are already deploying advanced technologies intended for explosives or narcotics detection," the report said. In Europe most airports send all passenger baggage through color X-ray devices that can detect many potentially dangerous objects ranging from handguns to bombs. "There have been tremendous enhancements with color X-rays," says Susan Rork, ATA's managing director for security. "Dangerous substances show up better." Many major European and Asian airports also use chemical-sniffing equipment--and trained dogs--capable of detecting some explosives. A few security innovations can actually save money: Air France is acquiring technology that will track every piece of baggage throughout its trip from the check-in counter to the aircraft hold. "In security terms, that means as soon as the passenger goes missing, the bag can be immediately taken off the plane, which is our major rule," says a Paris security official. "But it also means a decrease in lost baggage. Lost baggage means lost money, which is one reason this security system will pay for itself within a year and a half."

Price, however, is only part of the problem. The million-dollar CT-scanning equipment from InVision, after all, would come to only about $2 per passenger, a price most travelers would happily pay in return for greater safety. "There is a reluctance not only because of price, but because there has not been the awareness here of security that there is in Europe," says Sergio Magistri, InVision's president. "Security in Europe and the Middle East is the sole responsibility of the government. Here, responsibility is divided in many ways, from the airlines to the FAA to the airports themselves. The perception of threat here only recently began to climb."

After TWA Flight 800, the perception is likely to soar. But security specialists warn that improved flight safety means more than mere machinery, and that the U.S. is deficient in what analysts call the "security culture" of air travel. In Asian and European airports, the presence of a strong security apparatus is most strikingly visible in the form of soldiers guarding perimeters and patrolling passenger concourses, often dressed in body armor and carrying automatic weapons. Less obvious are the highly trained security workers who are usually government employees with civil service benefits and incentives to stay on the job. In the U.S. the work is frequently farmed out to private contractors who pay little more than minimum wage and have a high rate of employee turnover. European managers find that frightening. "The big fear is an element of collusion," says a former security officer at a major European airport. "If [terrorists] pay people enough, they will get on the plane." Such collusion was what allowed a group of Algerian hijackers to commandeer an Air France Airbus in Algiers on Christmas Eve in 1994, resulting in a 54-hour showdown during which seven people were killed. "In some countries, either economic or political factors ensure that it does not take much for someone to agree to look the other way," says Francois Grangier, an accident expert for France's National Union of Airline Pilots.

Sometimes looking the other way is the result of bad habits, not bad intentions. In a 1993 report, the Inspector General's office at the U.S. Department of Transportation found that security in four of the largest U.S. airports was "not adequate." Investigators, the report said, "were successful in 15 of 20 attempts" to gain entry to supposedly secure areas. "Once we gained access, we wandered around aircraft parking areas, baggage centers, maintenance areas and ramp administrative offices."

Simple boredom is another enemy of vigilance. "All it takes is a slight human error--a slump in attentiveness, a feeling of fatigue--for the system to falter," says Roland Jacquard, president of the International Observatory on Terrorism, an independent group based in France that tracks terrorism. An FAA technical report warns that even the most sophisticated equipment relies on the attention and skills of a human to prevent disaster. "The operator, presented with a previously unknown and visually complex object, has only seconds to analyze it before the next image comes along," the report says. "In these few seconds, the operator must decide if the luggage contains that rarest of items--about one in a billion--an explosive device."

Arrayed against those weary guardians are terrorists who may benefit from the financial aid and encouragement of renegade governments. "Techniques and technology today are very sophisticated," says Jacquard. "Terrorist groups and engineers are trained in camps in Iran or Libya by top-level technicians, often recruited from the former East Bloc nations. They are capable of building miniature bombs and detonators as small as a button."

The standard for comparison for any airline security system is Israel's El Al, which is both an obvious target of terror and the airline that has been the most successful in keeping passengers safe (at least one of the new CT-scanning devices, significantly, is at Ben Gurion airport). Since its security system of vigorous screening went into effect following the hijacking of an El Al flight to Algeria in 1968, no El Al plane has been successfully hijacked. Luggage is often hand-searched by agents who squeeze toothpaste tubes, empty pill containers and peer inside socks. The airline maintains a separate, protected check-in area equipped with special rooms for searching passengers who arouse suspicion. But the real heart of the El Al system is in interviews by security personnel who grill each passenger with a series of probing questions designed to elicit discrepancies or evasions. The purpose is less to nab terrorists--security is so daunting that few try to penetrate it personally--than to find innocent passengers carrying items given to them by terrorists. Isaac Yeffet, a former director of worldwide security for El Al, recalls a case in which a German passenger who thought he was smuggling drugs was actually carrying a bomb that could have killed himself and all his fellow passengers.

The FAA's policies in large part reflect the views of American passengers. Economy-class El Al passengers are required to check in a full three hours before flight time, and even business-class ticket holders must be there two hours early. "Will the American public be willing to sit there for hours and hours just waiting?" asks Louis Rodrigues, who led the gao's inquiry into FAA security policies. So far, Americans have firmly resisted the "El Al-ization" of their air travel. The tragedy of TWA Flight 800 could begin to change their minds.

--Reported by Bruce Crumley/Paris, William Dowell/New York, Nina Planck/London and Mark Thompson/Washington